Is 18mm ply enough?

[steviewonder]

I've bought some 18mm WBP ply to replace the floorboards in a bathroom approx 2.5 x 2m. The floorboards were less than 18mm thick themselves and sat on joists that were about 400mm apart.

Having done some more reading it now seems that 25mm ply is better when floorboards are replaced. Given the ply I using is thicker than the original floorboards and I plan on over boarding with 6mm marmox boards, will I be ok or do I need thicker ply?

Thanks

 

[DHTiling]

18mm will suffice if you put noggings at 400mm centres to the joist runs.. these need to be at board edges etc for support as well.. but if the option is there , then 22mm would be my choice.

 

[Concrete guy]

25mm is better if it's a single layer.

Or two layers of 12mm ply staggered joints and glued with panel adhesive and screwed together is even better.

Noggins anywhere where a joint spans a joist.